用引导向量让大模型评委更识破欺骗性回答。

LLM-as-a-judge is widely used as a scalable substitute for human evaluation, yet current approaches rely on black-box access and struggle to detect subtle dishonesty, such as sycophancy and manipulation. We introduce Judge Using Safety-Steered Alternatives (JUSSA), a framework that leverages a model's internal representations to optimize an honesty-promoting steering vector from a single training example, generating contrastive alternatives that give judges a reference point for detecting dishonesty. We test JUSSA on a novel manipulation benchmark with human-validated response pairs at varying dishonesty levels, finding AUROC improvements across both GPT-4.1 (0.893 $\to$ 0.946) and Claude Haiku (0.859 $\to$ 0.929) judges, though performance degrades when task complexity is mismatched to judge capability, suggesting contrastive evaluation helps most when the task is challenging but within the judge's reach. Layer-wise analysis further shows that steering is most effective in middle layers, where model representations begin to diverge between honest and dishonest prompt processing. Our work demonstrates that steering vectors can serve as tools for evaluation rather than for improving model outputs at inference, opening a new direction for thorough white-box auditing.